Dr. Bowring observed, that this Report, like every report communicated by government agents, gave far too favourable a view of the mineral prosperity of France. Two of the institutions to which reference had been made the mining establishments of Bassin du Creussot, and the iron-works of Decazeville-were not merely losing, but ruinous concerns; and the latter had been forced to import pig-iron from England. The injurious effects of the perversion of French industry to branches of production, for which the country possessed no natural advantages, was evidenced by comparing the number of ploughs in an agricultural district of France, with a district of the same extent in England, and the result would show that our country had the advantage, in the proportion of five to one. The cottagers in France, as most travellers have observed, were generally destitute of carpenters' tools, nails, and other little implements necessary to economy and comfort. Though the French engineers talked of the increased productiveness of their mines, they did not add, that iron in France was from 51. to 71. per ton dearer than in England; and as 300,000 tons of iron are annually consumed in that country, it followed that the French were taxed to the amount of more than a million and a half annually, to afford speculators in mines an opportunity of ruining themselves. - Mr. Felkin considered it of vital importance to have a correct statistical account of our mineral and manufacturing resources published to the world. Though the speculations to which Dr. Bowring had referred, had proved ruinous to the projectors, yet they were not abandoned; and it would be idle to deny, in reference to the competitive

situation of England and France, that machinery and fixed capital, accumulated on a spot, must be worked, even at a loss; and he believed that the Manchester manufacturers had already felt such establishments to be a thorn in their side. The workmen of France were a patient, industrious, and temperate race. The state of the Savings' Banks in that country reflected great credit on the character of the operatives, and was calculated to gratify every person who, laying aside the prejudices and jealousies of country, was gratified by the progressive improvement of our race, no matter in what locality, as a triumph of philanthropy.

"On a new Day and Night Telegraph," by Joseph Garnett.

At

The paper on this subject was accompanied by a model, to exhibit the construction and method of working the telegraph, which it is proposed should consist of two ladders, about forty-one feet long, framed together at about twenty-four inches asunder at the bottom, and twenty at the top, so as to constitute the frame for the machinery. There are two arms, one at the top, the other about midway up the frame-work, counterpoised by weights, and worked by machinery, consisting of eight bevel mitre wheels. the bottom of the frame-work, is a dial plate, with a pointer, and the workman, in setting the pointer, brings the arm of the telegraph into the required corresponding position. The paper proceeded to describe the mechanical adjustments, and was accompanied by tables of the day and night signals, each of which contains fifty-six variations of the arms. The night signals are made by covering the lamps in a particular order. For instance, two vertical lamps covered designate twenty-two horizontal ones covered thirty-and so on.

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Description of an improved method of constructing large Secretaires and Writing Tables," by Thomas Sopwith.

The great loss of time to persons engaged in extensive official business, in consequence of the difficulty of arranging numerous sets of papers, and of obtaining access to them when so arranged, induced the author to take this opportunity of describing a table invented by himself, and which had been extremely serviceable to him. The principle is, that by opening a single lock, the whole of the drawers, closets, and partitions are opened. These are so disposed, also, as to admit of every thing being reached without the person stirring from his seat. They are all entirely closed again by a single spring lock. It would be impossible to convey a proper idea of this ingenious invention without sectional plans and elevations; but the President, and many present, expressed their

admiration of the arrangements, and of the convenience which such a table must be to every person engaged in an extensive correspondence, or having many sets of papers on various subjects. One contrivance is peculiarly worth mentioning. Within this case Mr. Sopwith hangs up his various keys. On any key being removed, a small counter-balance weight, or bolt, drops down, and remains down until the key is replaced. This bolt effectually prevents the closing of the case. If, then, the person should forget to replace the key which has been removed, he is immediately reminded of it, by being unable to close the case. The principle and contrivances are applicable to many various arrangements of drawers and partitions.

"On the Power of Economising and Regulating Heat, for Domestic Purposes," by George Webb Hall.

The author insisted on the necessity of having the backs of the fire-places vertical, and the apertures of the chimneys as contracted as possible; and he described the results of his experiments. One principle to be universally attended to in close fireplaces is, that the burning fuel be surrounded by a substance retentive of heat, and capable of radiating it back upon the fire itself. This is attained by covering the fire itself with a species of fire-brick, and only allowing a very small aperture for the escape of the heat thus forced off at the highest degree attainable, then to be economised by close confinement and regulation. The economy of heat when attained, consists in conducting the hot air through long and horizontal flues, so as to counteract as much as possible its tendency to ascend, which tendency is exactly proportional to the temperature. The author illustrated the preceding paper by details of the arrangements which he had adopted and alluded especially to the researches of Rumford on this subject.

Sir John Robison remarked, that he had paid considerable attention to this subject, and to its practical applications; but he had done nothing more than endeavour to follow out the principles which were laid down by Mr. Sylvester, in his account of Mr. Strutt's method of warming the Derby Infirmary. He would also call attention to the accounts in Loudon's Cottage Economy, and to two papers in the Architectural Magazine, (see Mechanics' Magazine, vol. 27, p. 12, 21, 47) the one by Dr. Ure, the other by Mr. Ritchie, on the subject of warming and ventilating. -The President remarked, that great care was requisite in all experiments on the above subjects, especially with reference to the heat of smoke in the flues. He had once observed the smoke, at two feet from the exit, to be 190° Fahrenheit, the water in the hot water apparatus being 260° Fahrenheit; the

slightest change in one damper caused the temperature of the smoke in the flue to fall almost immediately to 160° Fahrenheit, and that of the water to rise to 290° Fahrenheit. Thus, by a slight alteration in the damper, about 60° Fahrenheit was saved.

Sir John Robison, at a subsequent mee ing, stated that he had omitted to mention a circumstance, which he considered of peculiar importance to the lower orders. Mr. Strutt, of Derby, to whom the country owed so much, had some years ago expressed to him an opinion, that coal-gas would be found, by the lower orders, the cheapest fuel for cooking. This he had applied; and the whole apparatus, which might be considered as the converse of the Davy safety lamp, consisted in fixing a piece of wire-gauze at the extremity of a gas-pipe of about six inches diameter. He referred to the account in Loudon's Encyclopædia of Cottage Architecture, for some valuable remarks and directions on this subject. The wire-gauze was liable to be destroyed under a long-continued intense heat: this, however, was obviated by sprinkling a small quantity of sand upon it. Bulk for bulk, gas was more expensive than coal, but the former was more economical and convenient for occasional use, and the smaller operations in cooking. "Notices on the Resistance of Water,"by John Scott Russell.

Mr. Russell stated, that the observations he had to offer might be considered as a sequel to what had been given at the preceding meetings of the Association (see Mechanics' Magazine, vol. 27, p. 448). He and Sir John Robison had been constituted a committee to prosecute the investigation of the motion of waves, and other problems in hydrodynamics, the results of which would be given in the Physical section. But, as they went on, they had met with some results of great value to the practical man; of these he now proposed to give a brief acount. The general problem was, the resistance of a fluid to a floating solid. Now, this is a department of science of which we are avowedly ignorant; so much so, that some of our best vessels are acknowledged to be constructed by the rule of thumb, as it is termed that is, by knowledge gained from a repeated series of trials and errors, and not on any fixed scientific principles. It had been ascertained in previous investigations, that the action of a solid on the water is very different from the action of fluid when impinging on a solid. These actions had formerly been considered the same. The solid causes an elevation; the elevation puts the water in motion. Thus, the question of resistance resolves itself into that of the motion of waves. Waves are of various kinds. The laws of the great primary wave had been

laid down in previous communications. Its velocity depends simply on the depth of the fluid. The old law of resistance, as the source of the velocity, is too small so long as the velocity of the solid is less than that of the wave, but too great so soon as the velocity of the solid becomes greater than that I of the wave. Mr. Russell then detailed some experiments which had led to the above law, and from which it appeared, that the form of the vessel of least resistance depends as well on the velocity with which it is to move, as on the velocity of the wave; also, that the form which is best for moving with a velocity less than the velocity of the wave, may be worst for moving with a velocity greater than that of the wave. The consideration of the laws of this wave reconcile many of the discrepancies in experiments on

this subject. Mr. Russell then proceeded to describe some remarkable facts, which they had observed on the motion of the particles constituting this wave; the particles had a vertical and a horizontal motion, and the extent of the motion depended on the force of the wave. Another remarkable result is, that the ordinates of the vessel should correspond with the ordinates of the wave; a form so constructed would separate the water without any apparent elevation or white ripple, which was common to all other forms. The form is that which belongs to the wave, which is to move with the particular velocity of the vessel.

The accompanying diagrams will serve to convey a more distinct idea of the nature of the motion of the particles of the water.

Fig 1 shows the form of the wave, and the lines of translation of the particles during the transit; A a B the line of the wave; a a' a", bb' b" c cc", &c. lines of translation of the particles during the transit.

Fig. 2 shows how the lines of a vessel are to be formed so as to produce a displacement analogous to the displacement of the wave, and so move through the fluid with the least resistance.

"On the Printiples of Oblique Bridges," by P. Nicholson.

The oblique arch, an invention of comparatively recent date, has been rendered necessary by the general adoption of railways, and by the necessity which exists for their being carried forward in lines as direct as possible. The theory of this arch is attended with some difficulty, and the author lays down in this paper the principles by which the engineer should be guided. Five of the feces of each stone are to be prepared in such a manner that four of them recede from the fifth, and when the stones are arranged in courses, the surfaces of the fifth face form one continued cylindric surface, which is the intrados, and the other four faces form the

beds and ends of the stones in which they join each other. In every course two of the opposite courses of the first stone, two of the opposite surfaces of the second stone, and so on, form two continued surfaces throughout the whole length of each course, and the edge of each of these continued surfaces in the intrados will be a spiral line. If a straight line be drawn through any point in one of the spiral lines perpendicular to the axis of the cylinder, the straight line will coincide with that continued surface which is a bed of that course, and the straight line thus drawn will be a tangent to the curved surface of the cylinder at that point in the spiral line; the straight line then drawn will be perpendicular to another straight line, which is a tangent to the spiral line at that point. The intrados being developed, the spiral lines which form the edges of the courses will be parallel, and their distances equal, and the spiral lines which are the edges of the ends of the stones will be developed in straight lines perpendicular to those lines which are the developements of the spirals of the edges of the courses. From these principles a simple

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geometrical construction may be deduced, such as the workman can readily use. construct an arch on the above principle, it is only necessary to know the angle of obliquity of the acute-angled pier, the width of the arch within its abutments, the height of the intrados above the level of the springing, the perpendicular distance between the planes and the two faces, and the number of arch stones in each elevation. The author then detailed some examples illustrative of this method.

'Remarks on the Material and Mechanical construction of Steam Boilers," by W. Greener.

Mr. Greener is of opinion, that the accidents which happen to steam-boilers are principally due to defect in the material of which they are constructed; and he details several experiments made on slips of iron cut from plates of different quality. He found that slips cut latitudinally from a plate, bore less by 30 per cent. than slips of the same dimensions cut longitudinally; in some cases the difference was much greater. He also had immersed plates in a mixture of sulphuric acid and water, and found that the injury done in twenty-four hours varied from 6 to 15 per cent. of the original strength. Many boilers will stand so long as the form remains perfect; but should any part, as the crown of the arch in cylindrical boilers, collapse, an accident is inevitable.

A communication was read from Mr. Maule, "On a Substitute for the Forcing Pump in supplying Steam-Boilers, &c." It was the well-known contrivance of a hollow cock, having an orifice, which, being uppermost, the plug became filled with the liquid, and then, being turned half round by the motion of the piston, the liquid could run into the vessel below.

Sir John Robison explained a model of the bucket of a pump in use in Sweden, the peculiar feature of which was, that the pressure of the sides of the bucket outwards against the pipe is exactly proportional to the load to be raised. This bucket is peculiarly applicable for raising foul water.

"A New Rotatory Steam-Engine," by S. Rowley. (See Mech. Mag. No.784.)

The inventor being absent, Mr. Evans undertook to bring this before the section; and having pointed out the construction, stated, that the only novelty in this consisted in the eccentric being on the inside. Many present condemned the rotatory engine as mechanically impracticable. Many of the most talented mechanics in this country had given up the attempt after repeated trials. It was argued, that no theoretical advantage can be gained by it; and that though there might be some circumstances under which economy of space and first cost were of such import

ance that the most expensive wear and tear can be borne, yet no prudent man would purchase an engine which might ruin him in the repairs. It is not sufficient to have a good theory; the powers of mechanical construction must be considered. Many inven

tions which, thirty years ago, might have been lost, because they were antecedent to the march of the mechanical art, would now, in the wonderfully advanced state of this art, be generally introduced.

66

'Report on Railway Constants," by Dr. Lardner.

Dr. Lardner stated, that at the last meeting of the Association a sum of money had been voted for the purpose of ascertaining certain railway constants,-that is, the force of traction on a level plane; the resistance due to friction, to curves, to the atmosphere; how the force of the wheels and the carriages influenced the motion. He then explained the causes which had prevented the experiments being made, and that, consequently, he had nothing to report as experimentally determined on the above subject; but that he had that instant received a set of experiments on the above subjects, made, at his request, by Mr. Woods, the resident engineer of the Liverpool and Manchester Railway, a young man whose excessive modesty alone prevented his occupying the position which his talents could claim. Some of these results, especially those relating to the effect of the resistance of the atmosphere, he then alluded to. He then described the various methods which had been proposed for the determination of the constants in question. These differed in no respect from the statements which were made last year at Liverpool, and which were then fully reported in our pages. (See Vol. 28, page 76.) He also described a dynamometer, by which the traction might be measured with considerable accuracy; and concluded by adverting to the great experiment which was now trying on the Great Western Railway, with respect to the gauge of seven feet instead of four feet eight inches.

Tuesday evening was devoted to the description and explanation of some of the most remarkable mechanical models, exhibited during this meeting at the rooms of the Central Exchange; but it was not known until a late hour.

Professor Babbage, said, that when at Berlin, ten years ago, he was present at one of the German Associations, in which the sciences and arts were equally represented; and so delighted was he, that he laboured to impart a share of his pleasure to his friends, and from the letters he then wrote, the first impulse was taken, which led to the formation of the British Association. The

models collected in the exhibition room were interesting, not merely to the mechanist, but to the higher classes, for it must be a great source of pleasure to know how the various articles of luxury and ornament were produced. The subjects which he had undertaken to illustrate, were the arts of engraving on copper and wood, and of taking impressions from hollow and raised plates or blocks. He then showed my models and diagrams, that the great difficulty in wood engraving or the raised die, was to obtain black lines crossing each other, and in copper-plate to obtain white lines crossing each other. Having noticed various mechanical contrivances for overcoming these difficulties, he described the art of printing in colours from wood blocks, and directed the attention of the members to specimens sent to the model room by Mr. Knight, declaring that the exertions of that publisher were likely to bring all the processes of wood engraving to a degree of perfection without parallel and beyond expectation. He then mentioned Mr. Woone's process, by which, in the raised die, black lines crossing each other had been obtained; a polished brass plate was thinly covered with plaster, and on this surface the process of sunk engravings could of course be easily performed, and then by taking a cast, the raised engraving might be obtained. He directed attention to the advantages resulting from the multiplication of engravings by the stereotype process, and particularly mentioned its application to the representation of the parts of machinery in detail. The Professor concluded by directing attention to a detector lock, which had been placed in the model room, but stated that its merits could only be understood by inspection.

The Rev. Dr. Robinson, of Armagh, then addressed the meeting. He felt great difficulty, he said, in following a person of such eminence as the President of the Mechanical Section; but when he looked at the model which he had undertaken to illustrate, that of the wooden viaduct over the Ouseburn, he felt that its architect was fairly entitled to the reward offered by the tyrant of old for the invention of a new pleasure. The stupendous edifices of Egypt, the splendid architecture of Greece, when compared with a bridge, were but specimens of magnificent barbarity. Although the art of constructing bridges had been long known, yet recent events had given it new developements; the destructive agents, fire and water, had been pressed into our service, and compelled to minister to our wants: like the evil spirits in the Arab tales, they had been forced to become slaves of the

lamp and the ring, and to obey the behests of the magician. Dr. Robinson then entered into a minute history of the various contrivances employed for bridges, which he illustrated by models, from the simple plank and rope, to the bridge of Schaffhausen, and the structure over the Ouseburn. In the latter, he said, a new element had to be provided for; the architect had not only to provide for the transit of weight, but for that of bodies coming with the velocity of the lightning, and the resistless force of the thunderbolt; stone could not be used in its construction, for the extensive mines in the vicinity might render the foundation insecure iron was so elastic that it might suddenly break from the intensity and rapidity of the shock given by the locomotive engines. He then pointed out all the contrivances in the structure for the distribution of stress, assigning the use of almost every beam. He said that many might be inclined to lament that such an edifice had been built with perishable materials, but by a recent discovery-which, perhaps, more than any other, illustrated the connexion between the sciences-wood had been rendered durable. He then minutely described the Kyanizing process, with which, of course, our readers are familiar.

Professor Willis then exhibited a model of a new locomotive engine, and explained all its parts. The merit of the new engine consists in its having a contrivance for changing the direction of the valve without an excentric motion on the shaft.

Mr. Dent read a paper 66 On the Construction of a portable Mercurial Pendulum, accompanied by Experiments."

The mercurial pendulum having a glass cistern containing the mercury, is not well calculated for sending abroad. The use of glass is suspended, in the present case, by substituting a cistern made entirely of castiron, which not only possesses portability, but other advantages; for in this cistern the mercury can be boiled to expel the bubbles of air. Before adopting iron for the cistern, it was obviously necessary to ascertain, by repeated experiments, the effect of that metal on the enclosed mercury, as regarded variations in temperature, when compared with glass. In prosecuting these experiments, a remarkable effect of radient heat was observed on these materials, worthy of being brought before the Association, as well as the description of the new mercurial pendulum, to the construction of which these experiments were subservient. The cistern is made entirely of cast-iron the adoption of this metal admitted of the cistern being turned perfectly cylindrical with

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